Enhancement of the Biological and Mechanical Performances of Sintered Hydroxyapatite by Multiple Ions Doping

In the present work, hydroxyapatite (HA) nanoparticles doped with Mg2+, Sr2+, and Zn2+ ions are developed by wet neutralization method and then sintered at 1,250°C to obtain bulk consolidated materials. Physicochemical and microstructural analyses show that the presence of doping ions in the HA structure induced the formation of βTCP as secondary phase, during the sintering process, and we found that this effect is depending on the stability of the various doping ions in the hydroxyapatite lattice itself. We also found that the formation of βTCP as secondary phase, in turn, confines the grain growth of HA induced by the high-temperature sintering process, thus leading to a strong increase of the flexural strength of the bulk materials, according to Hall-Petch-like law. Furthermore, we found that the doping ions enter also in the structure of the βTCP phase; besides the grain growth confinement, also the solubility and ion release ability of the final materials were enhanced. In addition to ameliorate the mechanical performance, the described phenomena also activate multiple biofunctionalities: (i) ability to upregulate various genes involved in the osteogenesis, as obtained by human adipose stem cells culture and evaluated by array technology; (ii) enhanced resistance to the adhesion and proliferation of Gram+ and Gram– bacterial strains. Hence, our results open a perspective for the use of sintered multiple ion-doped HA to develop ceramic biodevices, such as plates, screws, or other osteosynthesis media, with enhanced strength, osteointegrability, and the ability to prevent post-surgical infections

Making Space, Making Place: Digital Togetherness and the Redefinition of Migrant Identities Online

Immigrants have played a fundamental role in shaping the life and form of urban public spaces for generations. Their efforts, as many scholars have observed, mostly aimed at creating places of comfort in new and sometimes hostile receiving countries. In recent years, the combined contribution of the built environment and screen-based experiences have shaped migrants’ sense of community and belonging, thus making the concept of online community central to ideas about space and public life. Drawing upon a 3-year online ethnography, the article discusses to what extent new media constitute spaces of digital togetherness, where diasporic experiences and transnational identities are constructed and negotiated. It presents a transnational model of creative media consumption, which helps give insight as to how diasporas and ethnic minorities contribute to the transformation of public space in the Digital Age